Researches of regenerative medicine, cell transplantation and the like have started wherein human somatic stem cells or the like are cultured in a culture room under a clean environment and the cultured stem cells are transplanted into human body, to attain regeneration of damaged sites and therapy of diseases, and practice of these techniques have also started.
For maintenance-culturing human somatic stem cells used for the therapy and induction to differentiated cells (e.g., bone cells, adipocytes, myocardial cell and the like), an animal serum (e.g., fetal bovine serum, human serum or the like) is used. However, the composition of the animal serum is not fully clarified, and it is known that there is a risk that the animal serum may be infected by an unknown virus or prion.
Further, it is known that the growth ability of the cultured cells and performances such as differentiation inducing ability vary depending on the origin or product lot of the animal serum. Therefore, there is a problem in that it is difficult to attain constant performance of the maintenance culturing and constant quality of the differentiation-induced cells cultured in a medium containing a high concentration of an animal serum.
To avoid the risk of infection by an unknown virus or prion, the serum of the patient who is necessary to receive the cell transplantation is used in place of an animal serum in order to avoid the risk that the animal serum may be infected by an unknown virus or prion. However, in cases where the serum of the patient is used, it is necessary to collect a relatively large amount of blood from the patient, so that the physical burden of the patient is large, which is problematic.
In recent years, to make the influence by the origin of the animal serum or lot as small as possible, methods for differentiation induction in a medium containing a reduced amount of serum is used have been reported. For example, a method of differentiation induction of bone cells from mesenchymal stem cells wherein the amount of the added serum is reduced (Non-Patent Literature 1). Non-Patent Literature 1 is directed to an invention wherein mesenchymal stem cells originated from human bone marrow cells are cultured in a medium containing human serum, and discloses an example wherein the cultured human mesenchymal cells originated from human bone marrow cells are induced to a bone tissue in a differentiation induction medium containing human serum.
In the conventional methods of differentiation induction to bone cells from mesenchymal stem cells, β-glycerophosphate, dexamethasone, vitamin C and 10% animal serum are added (Non-Patent Literature 2).
Further, Non-Patent Literature 2 discloses a serum-free medium for culturing human embryonic stem (ES) cells, comprising a ligand for lysophospholipid receptor, that is, a ligand for endothelial cell differentiation gene (Edg) family receptors, such as lysophosphatidic acid (LPA), sphingosine 1-phosphate (S1P) or the like.